Thermionic valve circuits



Jan. 16, 1934. J ROUND r AL 1,943,459

THERMIONIC VALVE CIRCUITS Filed Feb. 2, 1924 BALANCING ...L. CAPACITY R2,HlGH RESISTANCE 0F EQUAL VALUE Snuentoz HENRY JOSEPH ROUND AND PETER W.WILL/W5.

Patented Jan. 16, 1934 UNETE STATES ATENT OFFICE Willans, Towcester,

England,

assignors to Radio Corporation oi America, a corporation of DelawareApplication February 2, 1924, Serial No. 690,220, and in Great BritainFebruary 5, 1923 6 Claims.

When a circuit is connected to the grid and filament of a threeelectrode valve and another circuit is connected to the anode andfilament, there is a possibility that the system may start oscillatingfor example owing to the fact that the capacity between the anode andthe grid furnishes an electrostatic coupling between these two circuits.This is particularly true if instead of a single valve several valvesare arranged in cascade.

U. S. Patent 1,334,118 to C. W. Rice shows how oscillation may beprevented by dividing the inductance of the grid circuit into twoportions by the lead from the filament instead of connecting I thefilament to the end of the inductance as is usual, and by connecting abalancing capacity between the anode and grid circuits.

According to this invention and with a view to preventing oscillation ofa valve we divide either the condenser of one or" the circuits or elsethe inductance of the anode circuit into two portions by the lead fromthe filament and we connect a balancing capacity between the twocircuits. According to this invention also we may employ as thebalancing capacity an unlit in a condenser of a difierent type.

In cases of cascade valve systems this anticoupling device can beemployed between each valve and the next, or in certain cases, here andthere along the valve system. Thus greater magnification can be employedthan was formerly possible.

Our invention is illustrated by the accompanying drawing in which Figs.1 and 2 are diagrammatic representations of different modificationsembodying the invention.

Fig. 1 shows an aerial circuit A connected to the grid G and filament Fof a valve whose plate or anode P is connected to an oscillatory circuit0 the capacity of which is divided into two portions C C1 by the leadfrom the filament. K is a burnt-out valve similar to the acting valveand inserted as a balancing capacity between the circuit 0 and the grid.

If the plate voltage changes current will flow across the condenserformed by the plate P and grid G of the valve through the coil A therebyimpressing an undesirable voltage across the grid filament circuit ofthe valve which will have the effect of disturbing the incoming signalsand it may even mask them together. This disturbing voltage iscompensated for by the condenser formed of the plate and grid of thevalve K which is connected between the grid of the main valve and thelower end of the net work comprising the coil 0 and the condensers C andC1. Owing to the symmetrical arrangement of this net work the platecurrent of the valve will cause currents in phase opposition to fiowthrough the condensers C and Cl and sufiicient current will be divertedfrom the condenser C1 by the unenergized valve K to exactly balance thedisturbing voltage resulting from the condenser action of the plate Pand grid (3-. This current will, of course, have the correct phaserelationship on account of the symmetrical arrangement of the circuitsand consequently any disturbances resulting from the action of the plateP and grid G as a condenser will be neutralized.

Fig. 2 shows an arrangement in which oscillation is prevented byconnecting the filament to a point near the middle of the inductance ofcircuit 0.

In this case a changing plate voltage will cause current flow across thecondenser formed by the plate P and grid G through the coil A and anequal and opposite current will flow through the coil A due to thepresence of the condenser formed by the plate and grid of the valve Kconnected as shown by the divided impedance 0.

In Fig. 3 the arrangement is similar to that in Fig. 1 except that thedivided condenser in this case is placed in the grid circuit instead ofthe plate circuit and two equal resistances R1 and R2 are shunted acrossthe parts of the diided condenser to assist in the neutralizing action.

Having described our invention what we claim 1. The combination with athree electrode valve of a circuit connected to the anode and containingtwo condensers, a connection from the filament to a point between thesaid condensers, a circuit connected to the grid and a pacity insertedbetween the two circuits to balance the capacity between the grid andanode of the valve.

2. The combination with a three electrode Valve of a divided capacityhaving a lead connected from the midpoint thereof to the cathode and anend connected to one of the other electrodes and a balancing capacityconnected between the other electrode and the other end of the capacitysaid balancing capacity having a value substantially equal to thecapacity between said other electrodes of the valve.

3. The combination with a three-electrode valve of a capacity in theanode circuit of the valve divided into two parts and having a leadconnected from its mid-point to the cathode and an end connected to theanode and a balancing capacity connected between the grid and the otherend of the capacity.

4. The combination with a space discharge device having an anode, acathode and at least one grid electrode, a circuit including threecapacities in series connected between the anode and the grid electrode,a connection from the cathode to a point between two of said capacities,one of said three capacities being formed so as to be equal to thecapacity between the grid elec trode and anode of the space dischargedevice.

5. The combination with a space discharge device having an anode, acathode and grid electrode, of a capacity in the anode circuit thereofdivided into two parts and having a lead connected from a pointintermediate said two parts to the cathode and an end connected to theanode, a balancing capacity connected between the grid electrode and theother end of the capacity, said balancing capacity comprising thecapacity existing between the anode and grid electrode of a spacedischarge device similar to the first named space discharge device.

6. The combination with a space discharge device having an anode, acathode and at least one grid electrode, a divided capacity arranged sothat a portion thereof is connected in the grid cathode circuit of saidspace discharge device while another portion thereof is connected in theanode, cathode circuit thereof, separate resistances shuntedacross therespective portions of the divided capacity, a coil shunted across theentire divided capacity, said coil having one end connected to the gridelectrode and the other end connected to the anode electrode, said lastconnection capacity.

HENRY JOSEPH ROUND. PETER WILLIAM WILLANS.

including a balancing

